Tattoo (or other kinds of skin pigmentation), either artificially implanted or traumatic-inflicted, relates to pigment deposition in the inner layer of skin. Laser treatment is considered to be one of the best tattoo removal methods because it is less invasive and has a very low risk (<5%) to cause scarring. The laser treatment method generally involves the utilization of a Q-switched laser to break down the large pigment particle into small molecules with its high energy pulses, which molecules are then removed by the scavenger cells of the body. One difficulty facing laser treatment method is that the treatment result is very hard to predict, especially for those artificial tattoos, since there are over 100 tattoo pigments used in the market and the exact composition of a given tattoo pigment is often kept as a trade secret by the manufacturer. Moreover, the treatment result may be influenced by the skin type of the patient, the depth of the tattoo pigment, the size of the pigment particle, etc. On the other hand, the patients often want to ‘see’ the expected result before laser treatment as the whole tattoo removal procedure (generally comprising several laser treatments) is both expensive ($1,000-10,000) and time consuming (up to 2 years). There thus exists a need for a diagnostic apparatus as an aid for laser tattoo removal, which can analyze the composition of the tattoo pigments and the photometric condition of the skin. Based on the acquired information, the diagnostic apparatus should be able to provide a set of parameters for optimizing the laser treatment procedure as well as to provide a simulated laser treatment result.